The present invention relates to stacking apparatus of the type used in the pallet manufacturing industry, for example. Such apparatus has as a principal function the formation of a vertical stack of pallets up to, for example, twenty such pallets which are delivered to the apparatus horizontally.
Existing stackers of the type with which the present invention is concerned require that the pallets being fed to the stacker be disposed such that the stringers extend transverse of the direction in which the pallets are delivered. In the case where the pallet assembly apparatus delivers manufactured pallets in a direction parallel to the stringers, each pallet must be turned ninety degrees before it can be fed into an automatic stacker of the type in the prior art. This can be inefficient and, if it requires additional equipment or manpower, costly.
The stacker of the present invention is designed to operate in close cooperation with a pallet assembly machine of the type disclosed in my copending, co-owned application, Ser. No. 11,204, entitled APPARATUS AND METHOD FOR ASSEMBLING PALLETS, filed Feb. 12, 1979. As disclosed in that application, an assembled pallet is delivered from the bottom of the machine in a direction parallel to the axis of the stringers. The apparatus of the present stacker includes a vertically reciprocating frame having two swinging end gates, referred to respectively as a headgate and a tailgate. The frame is reciprocated by a pair of scissors linkages which interconnect a base with the reciprocating frame. The scissors linkages are preferably powered by main pneumatic cylinders arranged with their axes in a vertical disposition.
With the reciprocating frame in a raised position, a pallet is received beneath the tailgate and the leading edge of the pallet is stopped adjacent the headgate of the reciprocating frame. The frame surrounds the periphery of the pallet when it is delivered to the stacker; and a switch responsive to a pallet in the fully delivered position actuates the main cylinders to retract and thereby lower the frame about the delivered pallet.
The headgate and the tailgate are each provided with lifter elements which extend into the spaces between deck boards and stringers and support the pallets already stacked by engaging the end, top deck boards of the lowest pallet in the stack. Thus, when the frame is lowered about the most recently delivered pallet, the partial stack of already-stacked pallets is also lowered and the weight of the partial stack is transferred to the most recently received pallet. After the weight of the stack is thus transferred, cam-actuated mechanisms cause both gates to swing outwardly so that the lifter elements swing about the top deck boards of the lowermost pallet so as to avoid obstruction.
When the frame is fully lowered, the same cam-actuated mechanism is released and the end gates are returned to their stacking positions. The return of the end gates may be assisted by springs, if necessary. Further, when the frame is in its lowermost position, a pneumatic limit switch is actuated to reverse the main pneumatic cylinders and thereby raise the frame and the partial stack of pallets, together with the most recently delivered pallet so that the apparatus is ready to receive another pallet beneath the new partial stack.
When a stack is formed to the desired height (or number of pallets in the stack), the delivery mechanism is actuated into an extended cycle and pushes the complete stack of pallets out of the apparatus in the same direction as the pallets had been delivered by rotating the headgate out of the way. After the stack of pallets is ejected from the stacking apparatus, the headgate is returned to its stacking position.
It will thus be appreciated that the present invention is designed to form a vertical stack from horizontally delivered pallets which are fed into the apparatus in a direction parallel to the length of the stringers and are also fed out of the apparatus in the same direction, as a continuation of the delivery motion.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.